PCA9600 Differential I2C Long Cable Extender with Buck Convertor

Product Description

Overview

This module is designed to enable long range I2C communications which extends the cable length from several meters to 300 meters. It is ideal for applications that need to run over long wires such as the CAT5e Ethernet cable that is commonly used to make connections between rooms. The signals are transmitted via balanced transmission lines (twisted pairs) which greatly reduces noise and extends the range. NXP PCA9600 I2C bus extender IC is used as the main component on this module. The PCA9600 is designed to isolate I2C-bus capacitance, allowing long buses to be driven in point-to-point or multipoint applications. It can operate at speeds up to at least 1 MHz.

The BUCK version of this differential I2C long cable extender module can be optionally connected to VBUS of the wire and convert the input voltage down to 5V.

Features

Bidirectional data transfer of I2C-bus signals

100 kHz operation on 300 meters of wire

1 MHz operation on 20 meters of wire

On-board buck converter

up to 36V power input

Plug and play design

The picture below shows the waveform of SCL and SDA when the sensor is directly wired to Arduino via a 15cm length cable. CH1(yellow) is SCL and CH2(blue) is SDA.

It could been seen from the picture above that the stray capacitance of the cable has seriously deformed the SCL waveform at both local(CH1) and remote(CH2) end.
Here comes the SCL waveform shows the performance of our differential I2C extender with Arduino, HDC1050, and 300m twisted pair cable.

and if give it a closer look, we can actually see the propagation delay of the SCL signal.

It could be read from the cursors in the picture the propagation delay of the SCL is about 1.76us. The propagation delay of the twisted pair cable is 4.8-5.3ns/m. GiveNthe length of the cable which is 300m, the propagation delay should be 1.4- 1.6us. There are also some delay beween the differential transceivers and some measure erros. So The 1.76us reading is quite reasonable.

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